Vitamin D and prevention of colorectal cancer

Abstract

Background Inadequate photosynthesis or oral intake of Vitamin D are associated with high incidence rates of colorectal cancer, but the dose–response relationship has not been adequately studied. Methods Dose–response gradients from observational studies of Vitamin D intake and serum 25-hydroxyvitamin D were plotted as trend lines. The point on each linear trend line corresponding to an odds ratio of 0.50 provided the prediagnostic Vitamin D intake or 25-hydroxyvitamin D concentration associated with 50% lower risk compared to <100 IU/day Vitamin D or <13 ng/ml serum 25-hydroxyvitamin D. Medians of these values were determined. Results Overall, individuals with ≥1000 IU/day oral Vitamin D ( p < 0.0001) or ≥33 ng/ml (82 nmol/l) serum 25-hydroxyvitamin D ( p < 0.01) had 50% lower incidence of colorectal cancer compared to reference values. Conclusions Intake of 1000 IU/day of Vitamin D, half the safe upper intake established by the National Academy of Sciences, was associated with 50% lower risk. Serum 25-hydroxyvitamin D of 33 ng/ml, which is known to be safe, also was associated with 50% lower risk. Prompt public health action is needed to increase intake of Vitamin D 3 to 1000 IU/day, and to raise 25-hydroxyvitamin D by encouraging a modest duration of sunlight exposure.